Programmable quantum emitter formation in silicon.

Silicon-based quantum emitters are candidates for large-scale qubit integration due to their single-photon emission properties and potential for spin-photon interfaces with long spin coherence times. Here, we demonstrate local writing and erasing of selected light-emitting defects using femtosecond laser pulses in combination with hydrogen-based defect activation and passivation at a single center level. By choosing forming gas (N2/H2) during thermal annealing of carbon-implanted silicon, we can select the formation of a series of hydrogen and carbon-related quantum emitters, including T and Ci centers while passivating the more common G-centers. The Ci center is a telecom S-band emitter with promising optical and spin properties that consists of a single interstitial carbon atom in the silicon lattice. Density functional theory calculations show that the Ci center brightness is enhanced by several orders of magnitude in the presence of hydrogen. Fs-laser pulses locally affect the passivation or activation of quantum emitters with hydrogen for programmable formation of selected quantum emitters.

Public health infection prevention: An analysis of existing training during the COVID-19 pandemic.

OBJECTIVES: In response to the COVID-19 pandemic, agencies and organizations required trainings to support the needs of the public health workforce. To better understand the training resources available, this study identified, organized, and classified infection prevention and control (IPC) training and educational opportunities. STUDY DESIGN: Environmental scan. METHODS: A total of 306 IPC training resources were compiled between January and April 2021. Key themes and topics were identified and compared to the Healthcare Infection Control Practices Advisory Committee's (HICPAC) core IPC practices. RESULTS: Three hundred and six training resources, including webinars, fact sheets, module-based learning activities, infographics, and professional practice guidance materials, were identified. Common themes included proper use of personal protective equipment (e.g., masks, gloves), community reopening guidance, and mass vaccination resources. A large proportion (74.9%) of trainings were under 60 min. Using the HICPAC framework, the most frequently addressed content included standard precautions (40%), leadership support (31.6%), and transmission-based precautions (25.8%). Few trainings addressed performance monitoring and feedback (17.1%). CONCLUSIONS: A wide range of organizations developed IPC-specific content during the pandemic. However, these resources did not address the breadth of knowledge required to implement IPC concepts effectively. The creation of universally applicable IPC core competencies and the development of high-quality IPC education and trainings for public health and the overall responder workforces should be prioritized. Accessible high-quality online and just-in-time trainings are critical for future pandemic and disaster preparedness.

Beam power scale-up in micro-electromechanical systems based multi-beam ion accelerators.

We report on the development of multi-beam radio frequency (RF) linear ion accelerators that are formed from stacks of low cost wafers and describe the status of beam power scale-up using an array of 112 beams. The total argon ion current extracted from the 112-beamlet extraction column was 0.5 mA. The measured energy gain in each RF gap reached as high as 7.25 keV. We present a path toward using this technology to achieve ion currents >1 mA and ion energies >100 keV for applications in material processing.

Absolute calibration of GafChromic film for very high flux laser driven ion beams.

We report on the calibration of GafChromic HD-v2 radiochromic film in the extremely high dose regime up to 100 kGy together with very high dose rates up to 7 × 1011 Gy/s. The absolute calibration was done with nanosecond ion bunches at the Neutralized Drift Compression Experiment II particle accelerator at Lawrence Berkeley National Laboratory (LBNL) and covers a broad dose dynamic range over three orders of magnitude. We then applied the resulting calibration curve to calibrate a laser driven ion experiment performed on the BELLA petawatt laser facility at LBNL. Here, we reconstructed the spatial and energy resolved distributions of the laser-accelerated proton beams. The resulting proton distribution is in fair agreement with the spectrum that was measured with a Thomson spectrometer in combination with a microchannel plate detector.

Design and implementation of a Thomson parabola for fluence dependent energy-loss measurements at the Neutralized Drift Compression eXperiment.

The interaction of ion beams with matter includes the investigation of the basic principles of ion stopping in heated materials. An unsolved question is the effect of different, especially higher, ion beam fluences on ion stopping in solid targets. This is relevant in applications such as in fusion sciences. To address this question, a Thomson parabola was built for the Neutralized Drift Compression eXperiment (NDCX-II) for ion energy-loss measurements at different ion beam fluences. The linear induction accelerator NDCX-II delivers 2 ns short, intense ion pulses, up to several tens of nC/pulse, or 1010-1011 ions, with a peak kinetic energy of ∼1.1 MeV and a minimal spot size of 2 mm FWHM. For this particular accelerator, the energy determination with conventional beam diagnostics, for example, time of flight measurements, is imprecise due to the non-trivial longitudinal phase space of the beam. In contrast, a Thomson parabola is well suited to reliably determine the beam energy distribution. The Thomson parabola differentiates charged particles by energy and charge-to-mass ratio, through deflection of charged particles by electric and magnetic fields. During first proof-of-principle experiments, we achieved to reproduce the average initial helium beam energy as predicted by computer simulations with a deviation of only 1.4%. Successful energy-loss measurements with 1 µm thick silicon nitride foils show the suitability of the accelerator for such experiments. The initial ion energy was determined during a primary measurement without a target, while a second measurement, incorporating the target, was used to determine the transmitted energy. The energy-loss was then determined as the difference between the two energies.

Source-to-accelerator quadrupole matching section for a compact linear accelerator.

Recently, we presented a new approach for a compact radio-frequency (RF) accelerator structure and demonstrated the functionality of the individual components: acceleration units and focusing elements. In this paper, we combine these units to form a working accelerator structure: a matching section between the ion source extraction grids and the RF-acceleration unit and electrostatic focusing quadrupoles between successive acceleration units. The matching section consists of six electrostatic quadrupoles (ESQs) fabricated using 3D-printing techniques. The matching section enables us to capture more beam current and to match the beam envelope to conditions for stable transport in an acceleration lattice. We present data from an integrated accelerator consisting of the source, matching section, and an ESQ doublet sandwiched between two RF-acceleration units.

A compact linear accelerator based on a scalable microelectromechanical-system RF-structure.

A new approach for a compact radio-frequency (RF) accelerator structure is presented. The new accelerator architecture is based on the Multiple Electrostatic Quadrupole Array Linear Accelerator (MEQALAC) structure that was first developed in the 1980s. The MEQALAC utilized RF resonators producing the accelerating fields and providing for higher beam currents through parallel beamlets focused using arrays of electrostatic quadrupoles (ESQs). While the early work obtained ESQs with lateral dimensions on the order of a few centimeters, using a printed circuit board (PCB), we reduce the characteristic dimension to the millimeter regime, while massively scaling up the potential number of parallel beamlets. Using Microelectromechanical systems scalable fabrication approaches, we are working on further reducing the characteristic dimension to the sub-millimeter regime. The technology is based on RF-acceleration components and ESQs implemented in the PCB or silicon wafers where each beamlet passes through beam apertures in the wafer. The complete accelerator is then assembled by stacking these wafers. This approach has the potential for fast and inexpensive batch fabrication of the components and flexibility in system design for application specific beam energies and currents. For prototyping the accelerator architecture, the components have been fabricated using the PCB. In this paper, we present proof of concept results of the principal components using the PCB: RF acceleration and ESQ focusing. Ongoing developments on implementing components in silicon and scaling of the accelerator technology to high currents and beam energies are discussed.

Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies.

The neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ∼1 eV using intense, short pulses (∼1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He(+) ions leads to more uniform energy deposition of the target material than Li(+) ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li(+) ions from a hot plate type ion source. He(+) beam pulses as high as 200 mA at the peak and 4 µs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. The accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.

Spirometry quality control: man versus machine

OBJECTIVE: To compare the efficacy of local quality control (QC) of BOLD (Burden of Obstructive Lung Disease) Trinidad and Tobago study with spirometer machine quality grades as well as with BOLD Pulmonary Function Reading Centre QC standards at Imperial College, London. METHODOLOGY: Quality of the randomly chosen two hundred spirometries was independently assessed by the local team based on the 2005 ATS/ERS spirometry standards. Central QC quality assessment results were blinded to the local team. However, the machine quality grades were readily available to both the central and local teams during interpretation. Local and machine QC performances were correlated with the central QC which was taken as the gold standard for this study. RESULTS: According to central QC, 17.5% of the spirometries were declared as unacceptable. The noted common errors were prolonged peak expiratory flow time(14.5%), submaximal blasts (11.5%), variable efforts (11%) and poor reproducibility (10%). Cronbach’s alpha assessment revealed an overall reliability of 0.82 and a correlation of 0.73 between central and local QC. The correlation between central and machine QC was poor(0.548). Local QC exhibited 89.1% sensitivity and 94.3% specificity relative to the central QC. Though the machine QC displayed a better sensitivity (97.6%), its specificity was significantly lower 45.7%). CONCLUSION: Local QC was effective when compared with the central QC and executed better performance than the machine’s QC. This expertise can now be utilized for the future spirometry based local research studies. Due to limitations in identifying various errors, machine QC should not solely be used as the determinant of acceptability.

Novel methods for improvement of a Penning ion source for neutron generator applications.

Penning ion source performance for neutron generator applications is characterized by the atomic ion fraction and beam current density, providing two paths by which source performance can be improved for increased neutron yields. We have fabricated a Penning ion source to investigate novel methods for improving source performance, including optimization of wall materials and electrode geometry, advanced magnetic confinement, and integration of field emitter arrays for electron injection. Effects of several electrode geometries on discharge characteristics and extracted ion current were studied. Additional magnetic confinement resulted in a factor of two increase in beam current density. First results indicate unchanged proton fraction and increased beam current density due to electron injection from carbon nanofiber arrays.

A tandem-based compact dual-energy gamma generator.

A dual-energy tandem-type gamma generator has been developed at E. O. Lawrence Berkeley National Laboratory and Sandia National Laboratories. The tandem accelerator geometry allows higher energy nuclear reactions to be reached, thereby allowing more flexible generation of MeV-energy gammas for active interrogation applications. Both positively charged ions and atoms of hydrogen are created from negative ions via a gas stripper. In this paper, we show first results of the working tandem-based gamma generator and that a gas stripper can be utilized in a compact source design. Preliminary results of monoenergetic gamma production are shown.

Mustard: a potential agent of chemical warfare and terrorism.

As one of the most important vesicant agents, the destructive properties of mustards on the skin, eyes and respiratory system, combined with a lack of antidote, makes them effective weapons. Such weapons are inexpensive, easily obtainable and frequently stockpiled. Sulphur mustard (mustard gas) has been used as a chemical warfare agent in at least 10 conflicts. In this article, the use of mustard as a potential agent of chemical warfare and terrorism is outlined. The dose-dependent effects of acute sulphur mustard exposure on the skin, eyes, and respiratory system are described, as well as the possible extents of injuries, the mechanisms of action and the long-term complications. Prevention and management of mustard exposure are briefly discussed. The need for awareness and preparedness in the dermatological community regarding mustard exposure is emphasized.

Integration of scanning probes and ion beams.

We report the integration of a scanning force microscope with ion beams. The scanning probe images surface structures non-invasively and aligns the ion beam to regions of interest. The ion beam is transported through a hole in the scanning probe tip. Piezoresistive force sensors allow placement of micromachined cantilevers close to the ion beam lens. Scanning probe imaging and alignment is demonstrated in a vacuum chamber coupled to the ion beam line. Dot arrays are formed by ion implantation in resist layers on silicon samples with dot diameters limited by the hole size in the probe tips of a few hundred nm.

European Convention on Human Rights: effects on psychiatric care.

The introduction of the European Convention on Human Rights into UK law will have a direct effect on practice in mental health care. The authors discuss developments associated with the Convention, examine different articles and suggest the changes they could bring. They suggest that, rather than reacting to the development of convention rights, healthcare professionals should take the opportunity to influence new standards for psychiatric care.

Biochemical and morphologic characterization of acrylamide peripheral neuropathy.

To determine whether reduced Na+/K+-ATPase activity might be involved in acrylamide (ACR)-induced peripheral axon swelling and degeneration, rubidium (Rb+) transport was measured as an index of enzyme function. x-ray microanalysis was used to quantify elemental Rb uptake and accumulation in internodal myelinated axons, mitochondria, Schwann cells, and myelin of rat tibial nerve cryosections. Results demonstrated impairment of Rb uptake in tibial axons from orally intoxicated (2.8 mM ACR for 34 days), moderately affected rats. In severely affected oral rats (49 days), complete inhibition of Rb transport and frank axon degeneration were evident. However, in moderate-to-severely affected rats exposed to ACR via ip injection (50 mg/kg/day for 11 days), neither structural nor enzymatic changes were present in tibial fibers. These findings in nerve cryosections suggested inhibition of axolemmal Na+ pump activity and degeneration were dependent upon route of ACR administration. This possibility was substantiated by a quantitative longitudinal morphometric study of conventionally fixed tibial nerve. Oral ACR treatment (2.8 mM ACR for 15-49 days) was associated with progressive axon degeneration, which was preceded by atrophy. Axonal swellings were rarely (<1%) observed. In contrast, ip ACR injection (50 mg/kg/day for 5-11 days) produced classic behavioral neurotoxicity but did not alter axon morphology in tibial nerve. Thus, fiber degeneration and decreased Na+ pump activity were consequences of subchronic oral ACR administration. This parallel expression suggests a mechanistic relationship. However, the corresponding general neurotoxicological significance is unclear since, behavioral toxicity induced by ip ACR develops without structural and enzymatic changes in tibial nerve.

Repeated use of Bacillus subtilis cell walls for copper binding.

Purified cell walls from Bacillus subtilis were repeatedly suspended in 5 mM CuCl2 and, after removing unbound Cu, were suspended in 1% (v/v) HNO3 to release bound Cu. The walls were then regenerated by washing in H2O. After five cycles, copper binding actually increased slightly, probably due to enhanced exposure of binding sites in the walls. Thus bacterial walls may be used repeatedly for metal removal during bioremediation of heavy metal pollution.

Cost-effectiveness analysis of extended conservative therapy versus surgical intervention in the management of herniated lumbar intervertebral disc.

The management of herniated lumbar intervertebral disc for patients not responding to an initial trial of conservative therapy is generally surgical. Little is known about the effect of continued conservative therapy on patients who have not improved or have deteriorated within the first 3 months. This study assessed which form of treatment, surgical or continued conservative therapy, is more cost-effective once an adequate trial of conservative therapy has failed. The study is a retrospective chart review of 55 white male truck drivers who presented with acutely herniated nucleus pulposus between 1985 and 1989. Twenty-five patients underwent surgery, and 30 underwent continued conservative therapy after initial rehabilitation. No significant difference was found in outcome (80% good or fair in both the surgical and conservative groups) or costs ($55,000 +/- $1,000/case during a 5-year period), hence no difference in the cost-effectiveness between the two treatment modalities (each $63,000 +/- $2,000/adjusted outcome). Conservatively treated patients, however, missed significantly more work. It was concluded that, for a patient not responding to the initial trial of conservative therapy, the option to undergo continued conservative treatment should be made available.

The efficacy and acceptability perindopril for the treatment of essential hypertension in a Caribbean population

Angiotensin converting enzyme inhibitors (ACEIs) are reported to have a lower efficacy in black hypertensive patients, particularly in monotherapy. However, no studies have examined the efficacy of ACEIs in a Caribbean population. A dose titration study was performed with perindopril in the English and Dutch Caribbean islands to assess the efficacy and acceptability of perindopril in this population. 435 patients with essential hypertension, with a diastolic BP between 95 and 125 mmHg were enrolled into this 3-month open study. Out of 333 patients who complete the study, 285 patients (69.3 percent) were successfully controlled (diastolic BP<90 mmHg). An additional 45 (7.81 percent) patients were controlled with the addition of hydrochlorothiazide 25 mg. Supine BP was reduced from 168.2 mmHg (ñ1.08) systolic and 105.6 mmHg (ñ0.48) diastolic to 149.12 mmHg (ñ0.98) systolic and 91.95 mmHg (ñ0.55) diastolic (p<0.001) after 2 months of perindopril in monotherapy. Supine BP was reduced further at the end of the 3-month treatment period to 144.3 mmHg (ñ0.91) systolic and 88.39 mmHg (ñ0.46) diastolic (p<0.001). There was no significant difference between the black population and the total population. Perindopril was well tolerated with a low reported incidence of cough. Withdrawal due to adverse events was also low at 2.3 percent (10 patients). The anti-hypertensive efficacy of perindopril in a Caribbean population and more specifically, the black Caribbean population with mild to moderate hypertension, is confirmed in this study together with its clinical and biological acceptability (AU)